Medical Physics Seminar – Friday, September 16, 2011

Franjo Pernus, Ph.D. (guest of Dr. Robert Jeraj)Professor and Head of the Imaging Technologies Lab Department of Electrical Engineering, University of Ljubljana

Medical imaging is currently undergoing rapid development with a strong emphasis being placed on the use of imaging technology to render interventions (surgery, radiotherapy, radiosurgery, interventional radiology, etc.) less and less invasive and to improve the accuracy with which a given intervention can be performed compared to conventional methods. In image-guided interventions, pre-intervention medical data, usually 3D computed tomography (CT) or magnetic resonance (MR) images are used to diagnose, plan, simulate, guide or otherwise assist a surgeon, radiotherapist, or possibly a robot, in performing an intervention. The plan is constructed in the coordinate system relative to pre-intervention data, while the intervention is performed in the coordinate system relative to the patient. The relationship or spatial transformation between pre-intervention data and plan and physical space occupied by the patient during intervention is established by registration. Registration, which is the crucial part of image-guided interventions, allows any 3D point defined in the pre-intervention image to be precisely located on the actual patient and may thus provide the radiotherapist valuable information about the position of the patient (targeted anatomical structure) or the surgeon about position of his instruments relative to the planned trajectory, nearby vulnerable structures, or the ultimate target. To be suitable for a clinical application, a registration algorithm must satisfy several requirements which concern registration accuracy, robustness, computation time, and complexity and invasiveness of intra-intervention data acquisition. An overview of 3D/2D rigid registration methods, the problem of their validation, and some quantitative registration results will be presented.